The present invention is directed to apparatus for automatically dispensing material from a roll. In particular, the invention is directed to an apparatus for automatically dispensing material from a roll for preselected time intervals which may be conveniently adjusted by the user.
Automatic material dispensing apparatus are well known in the art. For example, see U.S. Pat. Nos. 3,210,139, 3,301,617, 3,297,269, 3,167,367 and 3,167,368. Such apparatus, however, is not truly automatic. Thus, such apparatus typically employs a motor connected in series to an on/off switch for dispensing material for a length of time which must be supervised by the user. The on/off switch must be continually depressed by the user to ensure continuous operation of the motor. Dispensing of material ceases only when the user releases control of the switch to stop the motor.
Continuous supervision of the dispensing apparatus by the user is an annoyance which may, under certain conditions, become intolerable. For example, in a hospital environment, a disabled person may not be able to continuously maintain the on/off switch in the proper state for dispensing of the material. Similarly, under adverse visual conditions, it may be difficult to ascertain the length of material dispensed by the apparatus. The desired length of dispensed material may not be reached or may be exceeded by the time the user releases the on/off switch to stop the motor. If the user is sightless, or if the lighting conditions are insufficient to render the dispensed material visible to the user, it becomes impossible to operate the on/off switch to cause the desired length of material to be dispensed from the apparatus.
Heretofore, relatively complicated and costly time control circuits have been improvised to control the cyclic operation of a motor. For example, see U.S. Pat. Nos. 3,942,086 and 3,864,611. Such circuits require a proliferation of solid state control elements. Such circuits may be difficult to install in the limited space available in a material dispensing apparatus of the type described herein. Moreover, the repair of such circuits may be quite troublesome due to the large number of components utilized therein and/or due to the specialized operation of certain components as demanded by the intended application. For example, U.S. Pat. No. 3,942,086 requires a control circuit for operating a portable power tool motor for extremely precise time intervals which are less than the response time of the user. Such a control circuit requires separate motor trigger signal circuit and voltage clamping circuit controls to accurately operate the motor. In the control of an automatic material dispensing apparatus of the type disclosed herein, however, it is desirable to employ as few components as possible to attain economy of space and to render repair of the apparatus simple and inexpensive.
A primary advantage of the present invention is that it automatically dipenses a preselected length of material without intervention of the user other than initiating operation of the invention.
Another advantage of the invention is that it can be conveniently used by disabled persons and/or under adverse visual conditions.
A further advantage of the invention is that it is relatively simple in assembly and easy to install in the limited space available.
A still further advantage of the invention is that it is relatively simple and inexpensive to repair.
Other advantages appear hereinafter.